In control of the various electrical loads in airplanes, it is necessary to provide for selective energization of a large number of electrical switching devices for controlling the operation or positioning of elements such as the lights, landing gear, flight control surface, actuation, etc. The control station for these loads is usually located in the forward part of the aircraft in the cockpit or flight control station. The load busses are generally located in the wing roots and are thus quite remote from the control station. An extensive system of heavy gauge electrically conductive control wiring connects the control relays in the load circuits to the control station buss. Each of these control wires is normally protected by circuit breakers which are themselves quite heavy.
For control purposes, it is necessary to locate a control switch for each load at the flight station, and a relay or other power switching device at or near the point of power utilization. Local power busses furnish power to these loads and circuit breakers are used to protect the wiring against overloads and other faults such as short circuits in the power wiring. These circuit breakers must be of high current capacity to safely isolate the fault. Since the control wiring is similarly protected with circuit breakers without current limiting, high fault currents could also prevail in the control wiring. Consequently, a heavy gauge wire and insulation system has been required to protect against a fire or smoke hazard. Since the length of the wiring necessary between the control station and the large number of load stations is great, a necessary disadvantage is excessive weight and increased cost in the control wiring system.
It is accordingly an object of the present invention to obviate these disadvantages and to provide a novel method and improved electric power controller employing solid state construction and operable from a miniature gauge wiring system.
It is a further object of the present invention to provide a novel solid state power controller in the form of a solid state relay which incorporates the features of overcurrent (overload) protection, failure-mode detection logic, status monitoring and input control logic.
Still another object of the present invention is to provide a novel control system for airplanes employing such controllers of solid state construction and miniature gauge wiring.
Yet another object of the present invention is to provide a control system employing a novel and improved solid state controller system wherein solid state circuit logic control circuitry is operable to control two or more associated solid state power switching devices, thereby obviating the necessity for duplication of the expensive logic circuitry for each individual load.
Yet still another object of the present invention is to provide a novel method and system for providing current limiting in the source of the control power, i.e. the control circuit, for the switching of remote loads in the power circuit.
These and other objects and advantages will be apparent from the claims and from the following detailed description when read in conjunction with the appended drawings.